Marine Chemistry最新文献

{"title":"Carbonate and isotope chemistry in the outer Yellow River Estuary and beyond: Effects of flood and cold wave on interannnual variations in coastal stable carbon isotope","authors":"Zi-chen Liu ,&nbsp;Wei-dong Zhai","doi":"10.1016/j.marchem.2025.104486","DOIUrl":"10.1016/j.marchem.2025.104486","url":null,"abstract":"<div><div>The stable carbon isotope composition (δ¹³C) of dissolved inorganic carbon (DIC) traces many biogeochemical processes in large river estuaries and adjacent coastal seas. To better understand the dynamics of DIC and its isotope composition (δ¹³C_DIC) responding to floods and cold waves in the outer Yellow River Estuary and adjacent Laizhou Bay and central Bohai Sea, seven field surveys were conducted in summer and autumn of 2021 and 2022. Interannual variations in carbonate chemistry and δ¹³C_DIC were investigated. In the outer Yellow River Estuary, distributions of DIC and δ¹³C_DIC had little difference before and after an artificial flood, although water mixing dominates spatial variations of carbonate chemistry and stable isotopic composition in summer. The excess carbonate relative to a simplified two-endmember water-mixing was likely caused by the release of bicarbonate ions from the sediment and/or coastal wetlands over the Yellow River Estuary. In contrast, metabolic processes significantly affected the changes in DIC and δ¹³C_DIC in the adjacent central Bohai Sea. In 2022, δ¹³C_DIC in Laizhou Bay was lighter than that in 2021, while δ¹³C_DIC in the central Bohai Sea was heavier than that in 2021. This can be attributed to the wintertime super cold waves at the beginning of 2021 that affects the Bohai Sea and an unusual autumnal flood in 2021 that affects the Laizhou Bay. Both events make δ¹³C_DIC lighter (over half a year later) at given salinity with negligible changes in DIC concentrations. Our results also revealed that the lower reach of the Yellow River Estuary was a source of atmospheric CO₂ in summer. Although the quick transport of terrestrial nutrients caused by the artificial water-sediment regulation did not promote net community production soon, likely owing to high turbidity and relatively short residence time before our July cruises, the unusual autumnal flood likely transported much more nutrients into the Estuary and triggered algal blooms and turned it into a sink area of the atmospheric CO₂ in autumn. These findings provide fundamental information and new insights that support better understanding the complexity of the carbonate chemistry and isotope geochemistry dynamics in this ocean margin.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"269 ","pages":"Article 104486"},"PeriodicalIF":3.0,"publicationDate":"2025-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143128304","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Redox speciation of copper in the estuarine environment: Towards better understanding of copper water chemistry","authors":"Dora Crmarić,&nbsp;Saša Marcinek,&nbsp;Ana-Marija Cindrić,&nbsp;Dario Omanović,&nbsp;Elvira Bura-Nakić","doi":"10.1016/j.marchem.2024.104471","DOIUrl":"10.1016/j.marchem.2024.104471","url":null,"abstract":"<div><div>An adapted solid-phase extraction method was used for Cu redox speciation in the dissolved fraction in the stratified Krka River estuary in March and July 2023 at a “clean” and a “polluted” site, while anodic stripping voltammetry in differential pulse mode was used for Cu determination in the Cu(I), Cu(II) and Cu_T fractions. Overall, [Cu(I)]/[Cu_T] was significant in the Krka River estuary and varied between 20.7 and 88.7 %. At the “clean” site E1, the surface maximum of [Cu(I)]/[Cu_T] was observed in March. This was assumed to be related to the biological activity of the freshwater biota, as the temperature rose in March (compared to the previous winter months) and the salinity was low. On the other hand, at E1 in July, the maximum of [Cu(I)]/[Cu_T] was observed at the halocline and corresponded to the highest biological production thus we hypothesised it to be the result of Cu(I) complexation with ligands of biological origin. The minimum of [Cu(I)]/[Cu_T] was observed at the surface at E1 in July where terrestrial humic-like substances were present with higher affinity for Cu(II) than for Cu(I). At the “polluted site” E2 high [Cu(I)]/[Cu_T] values were observed at both the surface and the halocline in March. However, [Cu(I)]/[Cu_T] maximum was observed at the halocline at E2 in July and was associated with the highest biological production, as also observed at E1 in July. Nevertheless, the stabilisation of Cu(I) by chloride should not be disregarded as it maintained relatively high [Cu(I)]/[Cu_T] in the seawater layer at both stations in March and July. The fluctuations in [Cu(I)]/[Cu_T] occurred during the day at the surface at E2 in July, with the minimum of [Cu(I)]/[Cu_T] observed in the early morning, followed by an increase in [Cu(I)]/[Cu_T] during the day, indicating the importance of photochemical reactions in the Cu(I) formation and stabilisation.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"268 ","pages":"Article 104471"},"PeriodicalIF":3.0,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143177276","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Advanced deep learning technique for estimating global surface ocean calcium carbonate saturation (Ωcal)","authors":"Ibrahim Shaik ,&nbsp;P.V. Nagamani ,&nbsp;Sandesh Yadav ,&nbsp;Yash Manmode ,&nbsp;G. Srinivasa Rao","doi":"10.1016/j.marchem.2024.104483","DOIUrl":"10.1016/j.marchem.2024.104483","url":null,"abstract":"<div><div>The accurate estimation of surface ocean calcium carbonate saturation (Ω_<em>cal</em>) is crucial for understanding the impacts of ocean acidification (OA) on marine ecosystems, particularly for calcifying organisms. This study investigates the estimation of global surface ocean Ω_<em>cal</em> using machine learning (ML) models and satellite-derived data. Three ML models such as feed-forward neural networks (FFNN), random forests (RF), and Tabularnet (TabNet) were employed to estimate Ω_<em>cal</em>, utilizing in-situ and satellite measurements of sea surface temperature (SST), sea surface salinity (SSS), and Chlorophyll-a concentration (Chla). Among these, the TabNet model exhibited superior performance, with a root-mean-square error (RMSE) of 0.39, mean relative error (MRE) of 0.019, mean normalized bias (MNB) of 0.0058 and coefficient of determination (R²) of 0.96. SST showed a strong positive correlation with Ω_<em>cal</em> (<em>r</em> = 0.95), while SSS and Chla exhibited moderate positive (<em>r</em> = 0.49) and weak negative (<em>r</em> = −0.27) correlations, respectively. The study revealed significant spatiotemporal variability in Ω_<em>cal</em>, driven by seasonal changes and ocean circulation patterns. Sensitivity analysis highlighted the robustness of the TabNet model, maintaining high predictive capability despite variations in SST, SSS, and Chla. The TabNet model high accuracy provides a valuable tool for monitoring and forecasting changes in ocean chemistry, informing conservation efforts and policy-making. This study emphasizes the importance of advanced ML models in marine science and their potential for enhancing our understanding of global oceanic processes.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"268 ","pages":"Article 104483"},"PeriodicalIF":3.0,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143178166","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"QUODcarb: A Bayesian solver for over-determined datasets of seawater carbon dioxide system chemistry","authors":"Marina Fennell,&nbsp;François Primeau","doi":"10.1016/j.marchem.2024.104470","DOIUrl":"10.1016/j.marchem.2024.104470","url":null,"abstract":"<div><div>We present QUODcarb, a new solver for the CO₂-system in seawater, designed to handle any combination of system parameter measurements, whether exactly- or over-determined. QUODcarb, which stands for <strong>Q</strong>uantifying <strong>U</strong>ncertainty in an <strong>O</strong>ver-<strong>D</strong>etermined marine <strong>carb</strong>onate system, is formulated in terms of a Bayesian estimation problem. By combining prior thermodynamic information on the acid/base chemistry of CO₂ in seawater with measured parameters and their uncertainties, QUODcarb yields a probability distribution for the true CO₂-system state of a water parcel from which estimates of all system parameters with associated uncertainties can be obtained. By providing a single best estimate for the true CO₂-system state, QUODcarb enables a simplified, more accurate internal consistency analysis of the marine CO₂ system.</div><div>To demonstrate QUODcarb's utility, we analyze the GOMECC-3 dataset, that includes measurements of five CO₂-system parameters. A key finding is that by analyzing these high-quality, over-determined measurements with QUODcarb, we can achieve the GOA-ON 1 % uncertainty goal for carbonate ion concentration, even when accounting for the propagated uncertainty in the dissociation constants – a level of accuracy unattainable with exactly determined calculations. Using a single internal consistency metric, we rank 26 alternative measurement combinations, finding that (pH, <span><math><mi>p</mi><msub><mi>CO</mi><mn>2</mn></msub></math></span>) performs worst, while the combination with all five measurements performs best. Furthermore, the internally-consistent thermodynamic state estimates constrained by all five measurements fall within the range expected by the assumed measurement uncertainties for over 98 % of samples, with only minor adjustments to the dissociation constants, all of which remain within the reported uncertainties for their parameterized formulas.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"268 ","pages":"Article 104470"},"PeriodicalIF":3.0,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143178132","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Distribution, emission, and cycling processes of carbon monoxide in the tropical open ocean","authors":"Xuan Ji ,&nbsp;Ming-Liang Zhao ,&nbsp;Jie Ni ,&nbsp;Gao-Bin Xu ,&nbsp;Jing Zhang ,&nbsp;Gui-Peng Yang","doi":"10.1016/j.marchem.2024.104482","DOIUrl":"10.1016/j.marchem.2024.104482","url":null,"abstract":"<div><div>The carbon monoxide (CO) cycle in the marine mixed layer determines its emissions to the atmosphere and subsequently affects atmospheric chemistry and climate change. However, the contributions of oceanic CO transformation pathways and their impacting factors remain inadequately understood. Therefore, we investigated the distribution and cycle processes of CO in the Eastern Indian Ocean (EIO) and developed a CO budget model for the mixed layer. Surface seawater CO concentrations presented a diurnal variation due to periodic variations in solar radiation and rapid microbial consumption. The spatial distribution of CO in seawater was dominated by chromophoric dissolved organic matter (CDOM) and solar radiation. The EIO was a source of atmospheric CO and its daily CO emissions produced increases in the CO mixing ratio and hydroxyl radical consumption rate in the overlying atmosphere by 74.03 pptv and 6.48 pptv d⁻¹, respectively. Additionally, the budget model findings indicated that photoproduction (CDOM plus particulate organic matter), dark production, and phytoplankton emission accounted for about 67 %, 30 %, and 3 % of total CO production. The microbial consumption (94 %) and sea-air exchange (6 %) were the primary and secondary sink for CO within the mixed layer, respectively. Moreover, the photo-mineralization of dissolved organic carbon was estimated using CO as a proxy for CO₂ photoproduction. This study deepens our understanding of the oceanic CO cycle and the impact of photo-mineralization on the carbon cycle and is vital for refining global oceanic CO source-sink budgets and modelling studies.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"268 ","pages":"Article 104482"},"PeriodicalIF":3.0,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143178167","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Corrigendum to “Spatiotemporal variability in benthic-pelagic coupling on the Oregon-Washington Shelf” [Marine Chemistry Volume 268 (2025) Article number 104473]","authors":"Anna Hughes,&nbsp;Clare E. Reimers,&nbsp;Kristen E. Fogaren ,&nbsp;Yvan Alleau","doi":"10.1016/j.marchem.2024.104485","DOIUrl":"10.1016/j.marchem.2024.104485","url":null,"abstract":"","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"268 ","pages":"Article 104485"},"PeriodicalIF":3.0,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143178133","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Examining nickel limitation on urea utilization by phytoplankton communities in the subtropical Pacific Ocean","authors":"Mitsuhide Sato ,&nbsp;Shigenobu Takeda","doi":"10.1016/j.marchem.2024.104484","DOIUrl":"10.1016/j.marchem.2024.104484","url":null,"abstract":"<div><div>To test the possibility of nickel (Ni) limitation and nickel‑nitrogen (Ni-N) colimitation on phytoplankton growth, seven urea/Ni enrichment experiments were conducted in the subtropical and subarctic Pacific Ocean. Effects of additions of urea, nickel, and combination of urea and nickel were examined by monitoring the growth of the whole phytoplankton community and three different phytoplankton populations, <em>Synechococcus</em>, <em>Prochlorococcus</em>, and eukaryotes. In all the experiments in the subtropical regions, urea addition significantly increased the total chlorophyll <em>a</em> concentration as compared to the unamended control after two days of incubation, confirming widespread nitrogen limitation and high accessibility of the urea‑nitrogen to phytoplankton in the subtropical Pacific. In contrast, Ni addition did not affect the total chlorophyll <em>a</em> concentration, whether it was added alone or in combination with urea. To elucidate population-level responses to urea and/or Ni addition, cellular and population chlorophyll content and carbon content were estimated using flow cytometric parameters. <em>Synechococcus</em> and <em>Prochlorococcus</em> mainly responded to the urea enrichment. The addition of Ni alone did not show a significant effect on the chlorophyll or carbon content of any phytoplankton population in most of the experiments. Ni-N colimitation was evident only for <em>Synechococcus</em>, and not for <em>Prochlorococcus</em> or eukaryotic phytoplankton. Ni-N colimitation was evident in the urea drawdown rates only for one experiment out of the six experiments. In contrast, in the subarctic region, urea drawdown decreased with Ni addition, although the reason for this was unclear. The present study demonstrates that Ni bioavailability in the subtropical Pacific can evoke Ni-N colimitation in the pico-sized cyanobacteria <em>Synechococcus</em>, but it does not seem to affect phytoplankton biomass at the community level.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"268 ","pages":"Article 104484"},"PeriodicalIF":3.0,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143178169","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Biogeochemical cycling of dissolved Cu along the East Australian Current","authors":"Prayna P.P. Maharaj ,&nbsp;Pamela M. Barrett ,&nbsp;Michael J. Ellwood","doi":"10.1016/j.marchem.2024.104481","DOIUrl":"10.1016/j.marchem.2024.104481","url":null,"abstract":"<div><div>Copper (Cu) is an important micronutrient that is involved in multiple metabolic processes in marine phytoplankton. However, Cu concentrations that exceed an organism-specific tolerance level can be toxic. The measurement of stable Cu isotopic composition in seawater is an effective tool to better understand the biogeochemical cycling of this micronutrient in the marine environment. Here, we report the dissolved Cu (dCu) concentration and isotope composition of waters of the East Australian Current (EAC), the western boundary current in the south Pacific. The voyage was undertaken in 2018 during the austral spring as GEOTRACES process study GPpr13 consisting of a north-south transect categorised by the transition from warm, salty subtropical (ST) waters to the cold, fresh subantarctic (SA) waters in the Pacific sector of the Southern Ocean. The average dCu isotope composition (δ⁶⁵dCu) of the upper water column increased by ∼0.3 ‰ from north to south. The northern EAC stations generally had isotopically lighter dCu in surface waters, with mixed layer δ⁶⁵dCu values ranging from 0.25 ‰ to 0.31 ‰. Mixed layer δ⁶⁵dCu values ranged from 0.20 ‰ to 0.47 ‰ at the southern extension of the EAC and from 0.54 ‰ to 0.63 ‰ in the subantarctic zone. Generally, δ⁶⁵dCu profiles showed significant variability in the upper water column (200 m). The δ⁶⁵dCu composition was heavier at depths of chlorophyll <em>a</em> maxima, particularly for the high productivity stations, which can be attributed to either biological uptake and/or scavenging. A heavier surface δ⁶⁵dCu isotopic signature relative to deeper waters was also observed at stations with low chlorophyll <em>a</em> concentrations due to strong organic complexation of the heavy isotope in the upper water column. The deep ocean (≥2000 m) δ⁶⁵dCu at one of the subantarctic stations (station 10) was considerably lighter (0.25 ± 0.06 ‰), indicating a possible benthic supply of isotopically light Cu. This study provides a high-resolution δ⁶⁵Cu dataset, affording new insights into the biogeochemical cycling of Cu in the ocean.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"268 ","pages":"Article 104481"},"PeriodicalIF":3.0,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143177296","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Spatiotemporal variability in benthic-pelagic coupling on the Oregon-Washington shelf","authors":"Anna Hughes ,&nbsp;Clare E. Reimers,&nbsp;Kristen E. Fogaren,&nbsp;Yvan Alleau","doi":"10.1016/j.marchem.2024.104473","DOIUrl":"10.1016/j.marchem.2024.104473","url":null,"abstract":"<div><div>Continental shelf sediments are sinks for dissolved oxygen (DO) and sources of many major and minor nutrients required for oceanic surface primary production resulting in a strong coupling between benthic and pelagic biogeochemical cycling. In this study, we present paired benthic flux and bottom water biogeochemical data collected from two Oregon shelf sites sampled approximately quarter-annually between 2017 and 2019, and from nine other shelf sites, located off central Oregon to southern Washington, and sampled in either July or September 2022. The benthic fluxes were determined using a novel set-up for <em>ex situ</em> core incubations. When fluxes were normalized to the respective measured sediment DO flux, ratios aligned well with ratios of past flux estimates from the region which were determined using <em>in situ</em> benthic chambers; however, the <em>ex situ</em> flux magnitudes are generally lower. Our findings demonstrate sediments acting as net sinks for DO and nitrate, and sources for phosphate, silicate, and ammonium. Shelf-wide estimates of the relative contribution of sediment-remineralized phosphate and silicate to surface waters on the Oregon shelf, indicate that shelf sediments supplied at least 5 ± 7 % and 37 ± 7 % of the available phosphate and silicate during recent summer upwelling seasons, with similar, respective estimates of 2 ± 9 % and 35 ± 11 % during the spring. Remineralization ratios of C:N:P:O₂ corroborate increased denitrification during the summer and weak denitrification during the winter due to a more oxygenated water column in support of previous studies. A multi-tracer water mass analysis also exhibited an increased water-column nitrate deficit during the summer and fall. Benthic denitrification rates, estimated from benthic fluxes, were between 0.2 and 1.8 mmol N m^-2 day^-1 and in the range of past assessments during the upwelling season. A simple model, applied to further constrain the contributions to bottom water fixed nitrogen (N) loss under assumptions of benthic boundary layer height and residence time, showed that although sediment denitrification could readily account for total bottom water N losses during the summer, additional water-column denitrification is indicated by the strength of early fall deficits at some stations. Constraining water-column and benthic contributions to fixed N deficits is important for understanding how N-limited primary productivity in this region will respond to projected ocean deoxygenation under anticipated global warming. These results demonstrate the interplay of sediment and water-column remineralization processes across the OR-WA shelf. As in most shallow marine systems, the two are integral to the ecosystem dynamics and responses to environmental change.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"268 ","pages":"Article 104473"},"PeriodicalIF":3.0,"publicationDate":"2024-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142759097","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Nitrous oxide variability along an estuary influenced by agricultural land use (Guadalquivir estuary, SW Spain)","authors":"J. Sánchez-Rodríguez ,&nbsp;A. Sierra ,&nbsp;S. Moreno ,&nbsp;J. Forja ,&nbsp;T. Ortega","doi":"10.1016/j.marchem.2024.104467","DOIUrl":"10.1016/j.marchem.2024.104467","url":null,"abstract":"<div><div>The Guadalquivir Estuary is the largest estuary in the southwest basin of the Iberian Peninsula, which is subject to strong anthropogenic influence such as the damming or the multitude of crop fields on its margins. Nitrous Oxide (N₂O) variability is analysed considering the influence of temperature, salinity, water-atmosphere fluxes, benthic fluxes, reactivity and lateral inputs. N₂O increases along the salinity gradient, with values ranging from 5.9 to 103.3 nmol L⁻¹. Thus, values of N₂O concentration are very close to equilibrium with the atmosphere at the mouth, while in the inner zone the fluxes to the atmosphere are higher, showing the greatest variability of N₂O in the estuary (74.26 ± 7.41 μmol m⁻² d⁻¹). Sediments act as a source of N₂O to the water column, with benthic fluxes presenting a wide range from 2 to 20 μmol m⁻² d⁻¹. Denitrification processes in the sediments may be important in the inner part of the estuary, where negative benthic fluxes of nitrate have been observed. Production rates of N₂O in the water column are estimated from incubation experiments, resulting in higher production with temperature, and lower with salinity. Lateral inputs are calculated by balance of the different processes characterized and seems to be an important factor influencing N₂O variability in the inner zone of the estuary.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"267 ","pages":"Article 104467"},"PeriodicalIF":3.0,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142656456","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}